Apparatus for electronically squaring and summing projections of a vector for inspecting articles on a conveyor

ABSTRACT

Two mutually perpendicular light beam patterns are directed across a continuously moving conveyor toward an array of light sensitive devices arranged in pairs for inspecting the silhouette of articles on the conveyor. The leaner inspection circuitry includes a pulse generating and counting means capable of providing two signals indicative of the degree of lean of an article in two mutually perpendicular directions. These signals, or series of pulses, are squared, respectively, and then summed to be compared to some predetermined acceptable range.

United States Patent [1 1 Keller [4 1 Aug. 21, 1973 APPARATUS FORELECTRONICALLY SQUARING AND SUMMING PROJECTIONS OF A VECTOR FORINSPECTING ARTICLES ON A CONVEYOR [75] Inventor: Rene Keller, Dietikon,Switzerland [73] Assignee: Emhart Corporation S.A., Zurich,

Switzerland 22 Filed: Feb. 28, 1972 21 Appl. No.: 229,868

[52] US. Cl 235/151.3, 235/192, 250/223 R [51] Int. Cl. G06g 7/22, 006m7/00 [58] Field of Search 235/192, 190,191,

[5 6] References Cited UNITED STATES PATENTS 2,927,735 3/1960 Scuitto235/192 3,566,095 2/1971 Schrnitz 235/1935 X 3,598,978 8/1971Rernpert.... 235/1513 X 3,670,153 6/1972 Rempert 235/1513 X 3,671,7316/1972 Denoncourt et a1 235/192 Primary Examiner-Joseph F. RuggieroAttorneyJohn C. Hilton [57] ABSTRACT 3 Claims, 5 Drawing Figures45COMPARA10R Patented Aug. 21, 1973 2 Sheets-Sheet I.

FIG. 4

Lficosoc AmwlcosoC PusmvC APPARATUS FOR ELECTRONICALLY SQUARING ANDSUMMING PROJECTIONS OF A VECTOR FOR INSPECTING ARTICLES ON A CONVEYORBACKGROUND OF INVENTION Automated machinery is used increasingly for theproduction of articles in very large series. Frequently, the finishedarticles then proceed to an automated inspection line for checking thecritical dimensions and correct gauging of the articles and rejection offaulty or defect products.

In general, an automated inspection line comprises a conveyor to receiveand carry the articles in sequence and in a spaced relationship througha series of inspection stations. In order to inspect or check the shapeand the silhouette dimensions of the articles, it is known to usemechanical sensors or light barriers, the latter type being preferredbecause it provides for inspection without physical contact.

Correct positioning of the articles on the conveyor is a basicrequirement for operating an automated inspection line of the typedescribed above. Also, in the production of articles having a rotationalsymmetry it is usually required that the axes of such articles be in asubstantially vertical position relative to a horizontal base, such asthe conveyor which normally carries the articles on a horizontal face.U.S. Pat. No. 3,549,890 issued Dec. 22, 1970 to Rene Keller disclosessuch an arrangement for checking the position and, what is even moreimportant, any leaner, i.e., inclination of the axis of the rotationalsymmetry with respect to a vertical line, of the inspected articles. Theapparatus disclosed in the said patent comprises two first pairs oflight barriers including four light beams in a substantially horizontaland parallel alignment relative to each other. One pair of light beamsis arranged above the lower edge or bottom of the inspected article tobe tested while the other pair is arranged below its upper edge. Thehorizontal distance between the two light beams of each pair is smallerthan the diameter of the article at the corresponding height, and thedifference between the distance of the one pair of light beams and thecorresponding diameter of the article exceeds the difference between thedistance of the other pair of light beams and the corresponding diameterof the article. Each pair of light beams is connected with an electronicsignal generating means. The duration of the signal produced correspondsto the period of time during which both of the light beams of the pairof light barriers are interrupted by a passing article. In view of theabove ratio of the light beam distances to the diameters of theinspected article a signal from one pair of light beams is of longerduration than the signal from the other pair. Accordingly, parameter orleaner index can be obtained by comparing the relative time shift ordelay of the two signals. A

When the inspected article is in a vertical position the shorter signalis exactly at the center of the longer signal. On the other hand, whenthe inspected article is in an oblique position, that is a leaner, theshorter signal is not at the center of the longer signal but is shiftedfrom the center towards either end of the longer signal. In order tomeasure the relative shift of the two signals an impulse generatingmeans is provided with an impulse frequency controlled by the travelspeed of the inspected articles, i. e., the speed of the conveyor. Thelonger signal then is used to actuate an electronic gate to feed theimpulses produced by said impulse generating means to a counter. Theshorter signal is used to reverse the counter. If the tested article isin vertical position the shorter signal reverses the counter in themiddle of the longer signal, then the number of the impulses remainingin the counter is Zero at the end of the inspection of the article. Ifthe inspected article has a leaner or inclination relative to a verticalaxis the numbers of the impulses counted in and out of the counter arenot equal, and a residual number of impulses, either impulses counted inor impulses counted out, remains in the counter at the end of theinspection. The number of residual impulses in an index or parameterindicating the inclination or the leaner of the inspected article.

This method of leaner inspection by means of two light barriers isincapable of indicating leaners or inclinations in the direction of thelight beams. To avoid this limitation the device disclosed in the abovementioned U.S. Patent includes two pairs of light barriers in a mutuallyperpendicular arrangement and intersecting the direction of conveyormovement at an angle of 45.

Any leaner can be detected with this arrangement regardless of theleaner position relative to the conveyor. However, it is only theleaners in the direction of transport and transverse thereto that aremeasured at their normal value. In the patent disclosure a measuredvalue is considerd normal" if it is of equal size for both the first andthe second pair of light barriers. The determination of all otherleaners is subject to an error, the size of which depends upon the anglebetween the leaner plane and the light beams used for thisdetermination. Due to such errors a difference may appear between theleaner as measured and the actual leaner. Such an unprecisedetermination of the leaner of an inspected article is not asatisfactory solution of the technical problem defined above.

Accordingly, it is an object of this invention to avoid the abovediscussed shortcomings.

SUMMARY OF INVENTION The apparatus according to the invention forcomputing the squared value of the length of a vector from the doublelengths of the projections of said vector under angles of 45 and onto astraight line is characterized by an oscillator means and two electroniccircuits for continued addition, one input of each of said electroniccircuits being connected with said oscillator means while a second inputof each of said electronic circuits is connected with a device in whicha value corresponding to the double length of one of the two vectorprojections is stored, said device further having an output forsupplying a number of impulses correspond: ing to the square of thevalue stored in the said device, said apparatus comprising a summingcircuit connected with the outputs of said electronic circuits, saidsumming circuit having an output for supplying the sum of the squaredvalues. Said apparatus may further comprise a division circuit connectedwith the output of said summing circuit, said division circuit beingcapable of dividing said sum of said squared values by a constantdivisor, and said apparatus further comprising a counter means connectedwith said division circuit and being capable of receiving the dividedsum of said squared values.

When using this novel apparatus according to the invention incombination with a testing device of the type known and disclosed in theabove mentioned U.S. Pat.

No. 3,549,890 which is incorporated into this specification byreference, the actual or true leaner of an inspected article can bedetermined independently from the direction of such leaner.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic illustration ofan inspected article with a leaner relative to the vertical while thearticle travels between two pairs of light beams.

FIG. 2 is a schematic illustration of the signals produced by the twopairs of light beams of FIG. 1 upon passing through the inspectedarticle.

FIG. 3 is a graphic presentation of the counter position produced bysignals according to FIG. 2.

FIG. 4 is an illustration showing the lengths of projections of a vectoras a function of the angle between the vector direction and thedirection of projection.

FIG. 5 is a block diagram of a preferred embodiment of the apparatusaccording to the invention.

DETAILED DESCRIPTION With reference to the drawings, FIG. 1 shows aninspected article ll moving on a conveyor (not represented in thedrawing) in the direction of the arrow 13 and having a leaner relativeto vertical 12. Two pairs of light beams are arranged laterally relativeto the conveyor such that the light beams indicated at 15, I6, 17 and 18cross or intersect with the vertical plane of movement of the conveyor.Since each pair of light barriers produces a signal only as long as bothof the two corresponding light beams are interrupted by the movingarticle, and since the distance of the light beams of the one pair inrelation to the corresponding diameter of the article is selecteddifferently from the distance of the other pair, the two pairs of lightbeams generate sig nals of different duration. Because of the symmetricarrangement of the pairs of light beams relative to each other anarticle passing and interrupting the light beams produces signals (FIG.2) such that a shorter signal 23 appears enactly at the center of alonger signal 24 when the inspected article is substantially vertical.When the inspected article, as shown in FIG. 1, has a leaner orinclination relative to the vertical the degree of inclination or leanerbetween the two pairs of light beams corresponds to a horizontaldistance a and the shorter signal will be displaced from the center ofthe longer signal by the shift L (FIG. 2).

In the conventional testing devices of the type discussed above thelonger signal 24 controls the impulses fed into a counter. The frequencyof the impulses depends upon the speed of movement of article 11. Whenthe shorter signal 23a occurs the counting direction is reversed. Such acounting operation is schematically shown in FIG. 3 for a shorter signal23a which is shifted from the center of the longer signal 24 by adistance or shift L employing a counter with a self-actuated reversal ofthe counting direction as soon as the Zero position of the counter ispassed. It will be apparent that regardless of the actual degree ofinclination of the inspected article the counter position Z at the endof signal 24 corresponds to twice the value of shift L.

For the purpose of the above discussion it was assumed for simplicity ofpresentation that the leaner of article 11 and, accordingly, itshorizontal projection a are positioned in the direction of arrow 13 andtransverse to light beams l5, l6, l7 and 18. However, the articles onthe conveyor of a test line may have leaners in random directions. In anoperative testing device such as disclosed in the above mentioned U.S.Patent more than two pairs of parallel light barriers are provided,e.g., four pairs of light barriers in a crossed or mutuallyperpendicular arrangement. This is illustrated in FIG. 4 where the arrow13 represents the transport direction of a conveyor as discussed inconnection with FIG. I, while straight lines 31 and 30 intersecting witharrow 13 at angles of 45 and I35", respectively, indicate the directionsof the light beams of the crossed light barriers.

The horizontal projection of a leaner in a random direction isrepresented by the vector A which together with the arrow 13 defines anangle a. When an inspected article with a leaner is moved through thetesting line, this corresponds to, and will be indicated by, a shift ofthe vector A in the direction of arrow 13 through the light beamspositioned in the direction of line 30. In other words, vector A as seenby these light barriers has a length of L )t cos a )t sin a To the lightbarriers having light beams in the direction of line 31 vector It withthe same shift appears as having a length L )t cos a It sin a Because ofthe fact that counter position Z corresponds, as discussed above, totwice the amount of the shift L the counter positions for thecorresponding light barriers are Z =2L =2 )t(cosa-sina) For computingthe true length of projections h from the two counter positions Z and Zit is necessary first to eliminate the trigonometric functions. This canbe achieved by squaring the two sides of the above equations (1) and (2)(Z =4)t (cosa+sina)=4)t (l +2cosa-sin Upon addition of the two equations(3) and (4) it follows that A 123: lam/8 From either equation (5) or (6)it is apparent that the horizontal projections of a leaner can becomputed from the positions of the two counters cooperating with thepairs of light beams and that such computation yields the normal or trueleaner independently from the direction of the leaner.

Squaring of the counter positions and dividing of their sum can beefl'ected with relatively simple electronic means while electronicallyderiving the square root of this sum would require a far morecomplicated arrangement. Therefore, and in accordance with the inventionthe leaner is determined from the squared length of the horizontalleaner projection rather than directly from the length of thisprojection. The computation equation then is FIG. 5 is a block diagramillustration of an embodiment of an apparatus according to the inventioncapable of computing the above equation. This apparatus comprises anoscillator 40, the output of which is connected with the inputs of twodifferentiating networks 41 and 42. Two circuits 50 and 60 ofessentially the same structure are provided to square a given number. AnAND-gate 43 serves to sum up the squared values computed by the twocircuits. The apparatus further comprises a dividing network 44 fordividing the sum of the squared values by a fixed divisor, and a counter45 for receiving the result of the computing operation. However, itshould be noted that such a dividing step is not required to practicethe invention. It will be apparent that the network 44 might alsoinclude means for calculating the square root of its input. Each of thetwo circuits 50 and 60 includes two comparators 51 and 52, and 61 and62, two counters 53 and 54 and 63 and 64, a bistable flip flip 71 and72, as well as a gate circuit 55 and 65, all connected as indicated inFIG. 5.

To operate the apparatus for computing the squared value of the truelength of the horizontal projection of the leaner of an article,counters 46 and 47, each containing one of the numbers to be squared,are connected respectively with the second inputs 58 and 68. Provisionismade in the counter 45 to obtain a signal output whenever a presentnumber valueis reached. This signal then indicates that the leaner hasexceeded the permissible value.

In the operation of the inventive apparatus a testing device of the typeknown per se and disclosed, for example, in the above mentioned U.S.Patent, is combined with a testing line which supplies a signal, upontermination of the inspection of an article, through line 70 to set thebistable flip flops 71 and 72 which in turn open the AND gates 55 and65. The oscillator'generates an impulse sequence 73 in which the widthof the impulse preferably is equal to the distance between thesubsequent impulses. This impulse sequence is supplied to thedifferentiating networks 41 and 42. One differentiating network 41differentiates the leading edge of the impulse while the otherdifferentiating network 42 differentiates the trailing edge. Impulsesequences 74 and 75 then appear at the outputs of the twodifferentiating networks. These impulses have a symmetric shift inrelation to each other. These phase-shifted impulses are counted throughAND gates 55 and 65 and thence into 90 into the first counters 53 and 63respectively of the corresponding circuit 50 and 60, respectively, andsimultaneously fed through AND-gate 43 into dividing network 44. Thefirst counters 53 and 63 are compared with the counters 46 and 47 of thetesting device by means of comparators 51 and 61. Each comparatorsupplies an impulse to a second counter 54 and 64, respectively, as soonas the number of the impulses fed into the first counters 53 and 63corresponds to the counter position of counters 46 and 47 of theapparatus. Each of the second counters 54 and 64 is compared withcorresponding counters 46 and 47 of the testing device by means ofcomparators 52 and 62. As soom as the number of the impulses fed intothe second counters 54 and 64, respectively, reaches the counterposition of corresponding counters 46 and 47 of the testing device,comparators 52 and 62, respectively, provide signals to thecorresponding bistable flip flop circuits 71 and 72 so as to reset themthus closing the gates 55 and preventing further pulses from passingthrough. Accordingly, gate circuits 55 and 65 remain receptive only tosuch a number of impulses through lines 56 and 66, respectively, ascorresponds to the product of the counter position multiplied by itself,i.e., the squared value of the counter position of the coordinatedcounters 46 and 47, respectively. As a consequence of the phase shift ofthe impulses fed into circuits 50 and 60 these two products or squaredvalues can be added simply by means of AND-gate 43 and fed into dividingnetwork 44. For a computation in accordance with above equation (7) thesetting of the dividing network is selected such that only every eighthimpulse is fed into counter 45. The content of counter 45 thencorresponds to the target value, i.e., the squared value of the lengthof a vector having a random direction.

A detailed description of structure and function of the oscillator, thedifferentiating network, the electronic counters, the comparators, gatecircuits and dividing networks does not appear necessary because suchmeans are well known in the art. Any such means is commerciallyavailable, e.g., in form of modules, and can be used for tthe purposesof the invention.

It will be immediately apparent that it is possible, for example, tooperate without the differentiating networks 41 and 42 and to feedimpulses of identical phase into circuits 50 and 60. In this case,however, a relatively complicated adding circuit must be used instead ofthe simple AND-gate 43.

In the operation of the apparatus according to the invention asdiscussed above a comparator value can be fed from the presetting stagethrough line 49 into counter 45, which comparator value is or can berelated to the eight fold sum of the squared values of the two counterpositions. In this instance, the apparatus shown in FIG. 5 can beoperated without a dividing network 44.

It is understood that the apparatus according to the invention is notlimited to the use for computing the leaner of articles conveyed in atest line. Rather, the apparatus can be used for computing any problemswhich can be reduced to computing the square of the length of a vectorfrom twice the length of the projection of such vector under angles of45 and onto a-straight line.

I claim:

1. An apparatus for inspecting upright articles as they are advanced ona conveyor and comprising in combination two angularly related arrays oflight responsive means mounted respectively on opposite sides of theconveyor, means for directing a plurality of light beams toward saidlight responsive means, first pairs of light responsive means in saidrespective arrays disposed adjacent the surface of the conveyor, each ofsaid first pairs being horizontally spaced from one another a distancesignificantly less than the corresponding dimension of the base portionof an upright article, pulse generating means operable in timedrelationship to the speed of the conveyor for producing pulsesproportional in frequency to the speed of the conveyor, countersassociated with the outputs of said first pairs of light responsivemeans for recording the pulses produced during the outputs of said lightresponsive means, second pairs of light responsive means in saidrespective arrays and disposed above the first pairs at a spacing onlyslightly less than the corresponding dimension of an upper portion of anupright article, means for reversing said respective counters inresponse to the outputs of corresponding second pairs of lightresponsive means, discrete comparator means for producing output countsignals having two series of pulses, respectively, proportional innumber to the degree of lean of the inspected articles but beingunrelated in timed relationship to one another except as representinginspection of a single article, circuit means for squaring the number ofpulses in each series, and a summing circuit for adding said squarednumbers of pulses.

2. The apparatus of claim 1 further characterized by a divide-by circuitfor producing a quotient pulse count in response to the output of saidsumming circuit.

3. The apparatus of claim 1 further characterized by acomparator-counter which is preset with a total count of predeterminednumber, and which comparatorcounter produces a reject signal when theoutput of said summing circuit exceeds the preset total count.

1. An apparatus for inspecting upright articles as they are advanced ona conveyor and comprising in combination two angularly related arrays oflight responsive means mounted respectively on opposite sides of theconveyor, means for directing a plurality of light beams toward saidlight responsive means, first pairs of light responsive means in saidrespective arrays disposed adjacent the surface of the conveyor, each ofsaid first pairs being horizontally spaced from one another a distancesignificantly less than the corresponding dimension of the base portionof an upright article, pulse generating means operable in timedrelationship to the speed of the conveyor for producing pulsesproportional in frequency to the speed of the conveyor, countersassociated with the outputs of said first pairs of light responsivemeans for recording the pulses produced during the outputs of said lightresponsive means, second pairs of light responsive means in saidrespective arrays and disposed above the first pairs at a spacing onlyslightly less than the corresponding dimension of an upper portion of anupright article, means for reversing said respective counters inresponse to the outputs of corresponding second pairs of lightresponsive means, discrete comparator means for producing output''''count'''' signals having two series of pulses, respectively,proportional in number to the degree of lean of the inspected articlesbut being unrelated in timed relationship to one another except asrepresenting inspection of a single article, circuit means for squaringthe number of pulses in each series, and a summing circuit for addingsaid squared numbers of pulses.
 2. The apparatus of claim 1 furthercharacterized by a ''''divide-by'''' circuit for producing a quotientpulse count in response to the output of said summing circuit.
 3. Theapparatus of claim 1 further characterized by a comparator-counter whichis preset with a total count of predetermined number, and whichcomparator-counter produces a reject signal when the output of saidsumming circuit exceeds the preset total count.